The invention is in the field of casting of metals, specifically, the electromagnetic transferring of molten metals in the manufacture of metallic articles by casting, for example, by continuous metal-casting machines. And, for example, by periodically transferring measured, metered, controlled and/or predetermined quantities of molten metal into casting apparatus involving a succession of identical molds for producing a sequence or series of substantially identical metal castings. Novel methods, system and apparatus embodying the invention employ permanent magnets having reach-out magnetic fields to electromagnetically transfer, brake, measure and control the flow of molten metal.
The need for controlled flow of commercial quantities of molten metal is critical in the casting of metals in various kinds of casting apparatus in order to prevent either overflows or insufficiencies. For example, continuous controlled flow is advantageous for matching the flow rate of molten metal to the speed of a metal-casting device or machine into which the molten metal is being fed on a continuous basis. In the prior art, expensive tilting furnaces, launders, and servo controlled stopper rods are used. However, response to control signals in the prior art has been relatively sluggish, and maintenance may be costly. Moreover, each stopping of a continuous-casting operation may involve the dumping and remelting of much molten metal.
Smith et al. in U.S. Pat. No. 5,377,961 disclosed a device for ejecting small drops of solder onto a circuit board. Their device operated on a principle which goes back to Michael Faraday and Andr xc3xa9-Marie Amp xc3xa9re in the early nineteenth century. Faraday""s three-dimensional three-finger rule of induced electromotive force is exemplified also in the windings of electrical-machine rotors. This principle also is known as the Ampxc3xa9re-Lorentz law.
L. R. Blake and D. A. Watt, in their separate articles referenced above, describe pumps of similar principle used for pumping molten sodium or potassium as coolant through cores of atomic reactors. In their pumps, the electromagnet was very large and expensive and used an enormous flow of electrical current. Around 100,000 amperes were required to pump 2,000 gallons a minute of such very light liquid metal (Watt, pp. 98, 95).
Bykhovsky et al. in U.S. Pat. No. 5,009,399 used the Faraday principle. Their pressurizing zone was a disc-shaped, axially thin, circular cylindrical cavity in which molten metal was induced to swirl. An electromagnetic xe2x80x9csolenoidxe2x80x9d without moving parts was the source of unidirectional magnetism through the thin dimension of the cylindrical cavity.
Electromagnets and ordinary permanent magnets are drastically diminished in their magnetic flux density by an obstacle of even a small non-magnetic gap placed in their magnetic circuit.
My methods, system and apparatus embodying the present invention are applicable for electromagnetically impelling, transferring, braking, measuring and/or controlling the flow of substantial quantities of molten metal through a pressurizing conduit. Such flow of molten metal can be toward or into any suitable casting apparatus, for example, such as a continuous controlled flow into a continuous metal-casting machine as illustratively shown in FIGS. 1 and 1A. Also, such flow can be, for example, a periodic transfer of measured, metered, controlled and/or predetermined quantities of molten metal into suitable casting apparatus involving a succession of identical molds for producing a sequence or series of identical metal castings.
The Faraday-Ampxc3xa9re principle is employed, in the motor mode, by which electrical energy is converted into mechanical energy for usage most characteristically as a pump. The mode of operation is readily reversible for serving as a brake or throttle.
The prohibitive cost and huge bulk of an electromagnet for attaining the requisite magnetic excitation to bridge a large gap in the magnetic circuit is avoided by the use of permanent, high-energy xe2x80x9cneo-magnetsxe2x80x9d consisting of magnetic material which comprises a rare-earth element, for example such as neodymium. I have calculated that the coils themselves, i.e. the magnet-wire windings, of the most efficient configuration of an electromagnet of equivalent capability to that of rare-earth-containing, high-energy, permanent neo-magnets would occupy about 130 times the volume that are occupied by the neo-magnets. Moreover, the neo-magnets do not generate waste heat, whereas an electromagnet would generate considerable heat, due to passage of large amperage through electrical resistance of its windings.
The xe2x80x9creach-outxe2x80x9d capability of the neo-magnets positioned, oriented and arranged in specifically configured assemblies as shown and described enable, for the first time, an economically feasible, precise control of the flow of commercial quantities of molten metals. Such precise control makes possible the starting or stopping or adjusting of molten-metal flows almost instantaneously. There are no moving parts. The molten-metal flow area is enclosed, or is protected by an inert atmosphere and hence the flow avoids turbulent and corrosive contact with the atmosphere.
The method, system and apparatus optionally include an electromagnetic flowmeter. This flowmeter employs the Faraday principle in the generating mode, by which mechanical energy is converted into electrical energy. Thus, output of an electrical sensor indicates molten-metal speed and may be used to control pumping dynamics.